Method of manufacturing a horizontal thin film write, MR read head

ABSTRACT

A horizontal combined head is provided which has both a thin film write and an MR read element located at an air bearing surface (ABS). The read element can be formed with a track width that is independent of the track width of the write element. The MR sensor or the read element is separated from one of the first and second pole pieces of the write element by an insulation layer. Accordingly, the shields for the read element remain more stable after a write operation. In one embodiment of the present invention a single stripe MR sensor is employed while in a second embodiment a dual stripe MR sensor is employed. A method of the invention includes forming the dual MR stripe in a single process step so that the dual MR stripes of the dual MR sensor are near identical for implementing near absolute common mode rejection of noise.

RELATED APPLICATIONS

This Divisional Application claims priority of application Ser. No.10/688,726, filed Oct. 17, 2003 now U.S. Pat. No. 6,925,702, which was acontinuation of application Ser. No. 09/044,268, filed Mar. 19, 1998 nowU.S. Pat. No. 6,722,019, which was a divisional of application Ser. No.08/856,532, filed May 14, 1997 now U.S. Pat. No. 5,768,070.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a horizontal head with combined thinfilm write and MR (magnetoresistive) read elements at an air bearingsurface (ABS) and more particularly to a merged or piggyback horizontalhead wherein an MR sensor employs one or two MR stripes, the two MRstripes being uniquely formed for improved common mode rejection.

2. Description of the Related Art

A typical combined head includes a thin film inductive write element anda magnetoresistive (MR) read element. The thin film inductive writeelement includes one or more coil layers embedded in an insulationstack, the insulation stack being sandwiched between first and secondpole piece layers that extend into a pole tip region. A gap layer formsa write gap between the pole pieces in the pole tip region. The polepieces are magnetically coupled across a back gap in a back gap region.Between the pole tip region and the back gap region lies a yoke regionwhere the pole piece layers separate from one another to accommodate theinsulation stack. The insulation stack typically includes a firstinsulation layer (I1) on the first pole piece layer, one or more coillayers on the first insulation layer, a second insulation layer (I2)over the coil layer and a third insulation layer (I3) over the secondinsulation layer.

An MR read element includes an MR sensor sandwiched between first andsecond gap layers which are, in turn, sandwiched between first andsecond shield layers. In a merged head a single layer serves both as asecond shield layer for the read element and as a first pole piece forthe write element. In a piggyback MR head the second shield layer andthe first pole piece are separate layers. The merged (or piggyback) headis carried on a slider which, in turn, is mounted on a suspension in amagnetic disk drive. The suspension is mounted to an actuator whichmoves the head over selected tracks on a rotating disk for reading andwriting signals thereon. Rotation of the disk creates a cushion of airthat serves as an air bearing between the disk and the slider thatcounterbalances a loading force exerted by the suspension. A surface ofthe slider facing the disk is called an air bearing surface (ABS). TheABS is typically spaced from the disk in the order of 0.050 μm when thedisk is rotating. A combined head (that is, a merged or a piggybackhead) may be a “vertical” head or a “horizontal” head. In a verticalhead a major plane of the first pole piece layer is generallyperpendicular to the ABS, with edges of the first and second pole piecelayers exposed at the ABS. In a typical horizontal head horizontalcomponents of the first and second pole piece layers form a portion ofthe ABS so that edges of these layers are generally perpendicular to theABS and extend internally into the head without being exposed at theABS. In a horizontal head an insulation or gap layer separates the edgesof the first and second pole piece layers at the ABS.

In the vertical head, the MR sensor for the read element is located atthe ABS. In the horizontal head the edge of the MR sensor for the readelement is typically recessed from the ABS and receives read signals viaone of the pole piece layers which serves as a flux guide. Accordingly,the MR sensor, the first and second shields and the first and secondpole pieces are all in series. There are several problems with thisarrangement. First, it is desirable that the trace of a track being readbe narrower than the track as written. This is impossible with the priorart arrangement since the write gap also serves as the read gap. Next,each time a write operation is performed the shields are subjected to ahigh density of flux, which can render them unstable. As a result ofinstability, the magnetic domains of shield layers may not return totheir initial state, which can change the bias point of the MR sensorand result in inaccurate playback.

In both the vertical and horizontal heads it is desirable to increasethe signal-to-noise ratio during readback. This can be accomplished byemploying a dual stripe MR sensor wherein each MR stripe conducts anidentical sense currents During operation, both sense currents may beconducted to a differential amplifier in order to implement common modenoise rejection. If the read head collides with an asperity on amagnetic disk, noise generated by this collision will be reduced bycommon mode rejection. However, it is difficult to obtain near absolutecommon mode rejection because the MR stripes are typically formed inseparate process steps. When MR stripes are formed in separate processsteps they are not identical, due to slight differences in temperature,pressure, atmosphere and process times. In a dual stripe, vertical MRhead, the thin film layers of the read element are sequentially formedby separate process steps. Thus, there is a strong felt need to form thetwo stripes of an MR element in a single process step so that the twostripes are substantially identical, the better to implementnear-absolute common mode rejection of noise.

SUMMARY OF THE INVENTION

The present invention provides a horizontal combined head which has readand write elements located at the ABS. The read element is embodied inan MR sensor. The write element is embodied in a thin film structurewith a write gap. An edge of the MR sensor as well as the write gap arelocated at the ABS. This is accomplished by insulating the MR sensorfrom the first pole piece and spacing the MR sensor from the write gapalong the plane of the ABS. With this arrangement the track width of theread element may be less than the track width of the write head.

The present invention also provides a horizontal combined head includinga dual stripe MR sensor, wherein a pair of MR stripes are formed in asingle process step. This is accomplished by constructing an elongatedpedestal, depositing a layer of MR material on the sides and top of thepedestal, and then milling the MR material from the top of the pedestal,leaving an MR stripe on each side of the pedestal. The two MR stripesare substantially identical, thereby promoting near absolute common moderejection of noise.

An object of the present invention is to provide a horizontal head whichhas both of its read and write elements located at the ABS.

Another object is to provide a dual stripe MR sensor wherein the pair ofMR stripes are nearly identical to promote near absolute common moderejection of noise.

A further object is to provide a method of making a horizontal head withcombined read and write elements at the ABS.

Yet another object is to provide a method of making a dual stripe MRsensor wherein the pair of MR stripes are formed in the same processstep.

Other objects and many of the advantages of the invention will becomeapparent upon reading the following description of the invention takentogether with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a planar view of an exemplary magnetic disk drive;

FIG. 2 is an end view of a slider with a magnetic head of the disk driveas seen in plane II—II;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is a partial view of the slider and magnetic head as seen inplane V—V of FIG. 2;

FIG. 6 is a view seen in plane VI—VI of FIG. 5;

FIGS. 7A–7F are schematic cross-sectional side views illustratingvarious process steps employed in constructing the horizontal magnetichead on a substrate or slider;

FIGS. 8A–8M are schematic cross-sectional side views of the MR sensorportion of the horizontal head during various steps of its constructionwith the exception of FIGS. 8F and 8H which are isometric viewsillustrating steps during the construction;

FIG. 9 is a schematic diagram of the conductors for applying currents tothe coil layer of the write head and the MR stripe of the single stripeMR sensor embodiment;

FIGS. 10A–10M are schematic cross-sectional side views of a dual MRsensor during various steps of its construction; and

FIG. 11 is a schematic diagram illustrating the conductors for applyingcurrents to the write coil of the write gap and the pair of sensors ofthe dual MR sensor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views there is illustratedin FIGS. 1–3 a magnetic disk drive 30. The drive 30 includes a spindle32 which supports and rotates a magnetic disk 34. The spindle 32 isrotated by a motor 36 which in turn is controlled by a motor controller38. A horizontal combined magnetic head 40 for reading and recording ismounted on a slider 42 which, in turn, is supported by a suspension 43and actuator arm 44. A plurality of disks, sliders and suspensions maybe employed in a large capacity direct access storage device (DASD) asshown in FIG. 3. The suspension 43 and actuator arm 44 position theslider 42 to place the magnetic head 40 in a transducing relationshipwith a surface of the magnetic disk 34. When the disk 34 is rotated bythe motor 36 the slider is supported on a thin (typically, 0.05 μm)cushion of air (air bearing) by the air bearing surface (ABS) 46. Themagnetic head 40 may then be employed for writing information tomultiple circular tracks on the surface of the disk 44, as well as forreading information therefrom. Processing circuitry 48 exchanges signalsrepresenting such information with the head 40, provides motor drivesignals, and also provides control signals for moving the slider tovarious tracks. In FIG. 4 the slider 42 is shown mounted to a headgimbal assembly (HGA) 50 which in turn is mounted to the suspension 43.

The horizontal head 40 is shown embedded in the slider 42 in FIGS. 5 and6. The horizontal head 40 includes one or more oil layers 52 which areembedded in an insulation stack 54. The insulation stack 54 issurrounded by and sandwiched between first and second pole pieces 56 and58, the pole pieces 56 and 58 being separated by an insulative gap layer60 at the ABS and being connected at a back gap region 62. Accordingly,when a current is conducted through the coil layers 52 flux will fringebetween the first and second pole pieces across the gap 60 to writesignals into the magnetic disk 34 (FIG. 1).

The first pole piece 56 has a horizontal component 64 and the secondpole piece 58 has a horizontal component 66. The horizontal components64 and 66 are thin film layers which have major planar surfaces whichform a part of the ABS and which have edges 68 and 70 which aresubstantially perpendicular to the ABS. This structure distinguishes thehorizontal head 40 from a vertical head (not shown) which has thin filmedges of the first and second pole pieces forming a portion of the ABSand major thin film planar surfaces of the first and second pole piecesextending substantially perpendicular to the ABS. Horizontal andvertical magnetic heads should not be confused with horizontal andvertical recording in the magnetic media. Vertical recording means thatthe signals in the magnetic media are polarized perpendicular to thesurface of the media whereas in horizontal recording the polarization ofthe signals is parallel to the surface of the media. The first polepiece 56 has a recessed horizontal component 72 which is connected tothe horizontal component 64 by a slanted component 74 and the secondpole piece 58 has a recessed horizontal component 76 which is connectedto the horizontal component 66.

Exposed at the ABS is an MR sensor 80 which is sandwiched between firstand second gap layers 82 and 84. The first and second gap layers 82 and84 are sandwiched between edge surfaces of first and second shieldlayers 86 and 88. Major thin film surfaces of the first and secondshield layers 86 and 88 form a portion of the ABS. The horizontal head40 shown FIG. 5 is a merged MR horizontal head since the horizontalcomponent 64 of the first pole piece 56 and the second shield 88 of theMR head are a common layer. Optionally, the common layer can be twoseparate layers separated by an insulation layer so that the horizontalcomponent 64 of the first pole piece and the second shield 88 aremagnetically decoupled. This latter type of head is referred to as apiggyback MR head.

A pair of vias, one of which is shown at 90, extends through the slider42 and the insulation stack 54 for providing a current I to the coillayers 52 and a pair of vias, one of which is shown at 92, extendsthrough the slider 42 and the insulation stack 54 for providing a sensecurrent I_(s) to the MR sensor 80. The vias 90 and 92 are filled with aconductive material, such as copper, for conducting the currents. Thepair of vias, including via 90, terminate at exposed pads 94 and 96 andthe pair of vias, including via 92, terminate at exposed pads 98 and100, as shown in FIGS. 4 and 5. Conductors 102 and 104 are connected tothe pads 94 and 96 and conductors 106 and 108 are connected to the pads98 and 100 at first ends thereof and second ends of the conductors (notshown) are connected to the processing circuitry 48 shown in FIG. 3.

The present invention is distinguished by an insulation layer 110 whichis sandwiched between the recessed horizontal component 72 of the firstpole piece 56 on one side and the MR sensor 80, the first and second gaplayers 82 and 84 and the first and second shield layers 86 and 88 on theother side. This isolates the operation of the read head portion fromthe write head portion so that the read head portion can be located atthe ABS. This obviates the problem associated with employing one of thepole pieces as a flux guide for the read head which causes instabilityof the shield layers as well as the problem of coupling the track widthof the read head to the write head discussed hereinabove.

FIGS. 7A–7F show various steps in the construction of the horizontalcombined head with emphasis on the construction of the write and readelements. In the construction of the horizontal head a substrate 112 isprovided which, after construction of multiple heads thereon, is dicedinto individual sliders 42 with a respective horizontal head 40 carriedthereby. A layer of head compatible material, such as silicon dioxide,may be laid on top of the substrate 112. A layer of Permalloy 116 isthen formed on top of the layer 114, a first insulation layer 118 isformed on top of the Permalloy layer 116, the first coil layer 52 isformed on top of the first insulation layer 118, a second insulationlayer 122 is formed on top of the first insulation layer 118 and thefirst coil layer 52, a third insulation layer 124 is formed on top ofthe second insulation layer and the first coil layer 120, the secondcoil layer 52 is formed on top of the third insulation layer 124 and afourth insulation layer 128 is formed on top of the third insulationlayer 124 and the second coil layer 52. The Permalloy layer 116 and thecoil layers 52 may be formed by employing typical photolithographytechniques. The layers 116, 118, 122, 124 and 128 extend laterallythroughout a wide expanse of the wafer 112 and may be lapped after eachformation. Vertical components 130 and 132 of the first and second polepieces are formed in vias and joined to the Permalloy layer 116.Construction of a similar head is shown in a commonly assigned U.S. Pat.No. 5,408,373 which is incorporated by reference herein.

Insulation layers 118, 122, 124 and 128 form the aforementionedinsulation stack 54. On top of the insulation stack 54 there is formedan insulation layer 134, such as alumina, which extends over the entirewafer 112. As shown in FIG. 7B a resist layer 136 is formed on top ofthe insulation layer 134 and is patterned to provide an opening so thatthe insulation layer can be recessed by milling as shown in FIG. 7B. Aresist layer 138 is then provided, as shown in FIG. 7C, for recessingthe insulation stack on the right side and removing the insulation layeron the left side. As shown in FIG. 7D, a photoresist layer 140 withopenings is then provided for the deposition of the recessed horizontalcomponents 72 and the slanted component 74 discussed hereinabove. Asshown in FIG. 7E, a photoresist layer 142 is then formed with an openingso that the aforementioned insulation layer 110 can be formed.

The horizontal components 64 and 66 and the gap 60, shown in FIG. 7F,may be formed by typical photolithography patterning techniques or byside wall technology. If side wall technology is employed a rectangularbox of photoresist (not shown) may be formed on the insulation stack 54immediately to the left of the region where the gap layer 60 is to beformed. Insulative gap material is then deposited on the top of thephotoresist box as well as its sides. Milling is then employed to removethe insulative gap material from the top of the box exposing thephotoresist so that the photoresist can be removed by developing therebyleaving a rectangular fence of gap material, one side of the fence beinglocated at 60. Photoresist is then employed for patterning and formingthe horizontal component 66, after which this photoresist layer can beremoved and another photoresist layer is employed after patterning forremoving all portions of the insulative gap material except the gap 60.The horizontal component 64 may then be formed by photoresist patterningor side wall technology. Side wall technology formation of verticalcomponents will become more readily understood by the followingdescription.

FIGS. 8A–8L show the various steps in the construction of the readelement portion of the horizontal head, the read element portion beinglocated at the ABS. FIG. 8A shows the first step in the construction ofthe read head after the construction of the horizontal component 64shown in FIG. 7F. An insulative gap layer 150 is formed over the entirewafer including side walls, as shown in FIG. 8A, and then the topportions are removed by any suitable means, such as ion beam milling,leaving the side wall 84 which is the second gap layer of the read head.The formation of the layer 150 may be by plasma vacuum chemicaldeposition (PVCD) which covers not only top surfaces but also the sidewalls. This process of covering an entire wafer, including side walls,with a deposition followed by milling of the top surfaces is generallyreferred to as the aforementioned side wall technology formation ofcomponents. It should be understood that these components can bealternatively formed by typical photo-lithography techniques.

A layer or layers 152 of MR material is then deposited, as shown in FIG.8C, and the top portions are milled away, as shown in FIG. 8D, to formthe MR sensor 80. It should be understood that the MR sensor 80 may bemultiple layers of a soft adjacent layer (SAL), an insulation layer, anMR stripe and a capping layer as desired. A photoresist layer 154 isthen formed in the active region of the MR sensor, as shown in FIGS. 8Eand 8F, and hard biasing and lead layer material 156 may be deposited asshown. The photoresist 154 is then removed and photoresist 156 is placedto protect hard bias and lead material which is to be retained, as shownin FIGS. 8G and 8H, after which the top hard bias and lead material ismilled away to leave first and second lead layers 158 and 160. Thephotoresist layer 154 is then removed and a layer of gap material 162 isformed as shown in FIG. 81. Photoresist 164 is then placed to protectthe gap material to be retained and top portions of the gap material areremoved by milling, as shown in FIG. 8J, leaving the first gap 82. Thephotoresist 164 is then removed and first shield material layer 166 isformed as shown in FIG. 8K. Photoresist 168 is then formed and the topof the second shield material layer is then removed by milling as shownin FIG. 8L. The photoresist layer 168 is then removed leaving the firstshield 86.

FIG. 9 is a schematic diagram of the conductors for the write and theread elements of the single stripe MR sensor embodiment of thehorizontal head. Conductors 170 and 172 are connected to opposite endsof one or more of the coil layers 52 wherein one of the conductors suchas conductor 170 may be grounded and the other conductor 172 may receivea current signal I. Conductors 174 and 176 may be connected to oppositeends of the active region of the single MR stripe of the sensor 80wherein the conductor 174 may be grounded and the other conductor 176receives a sense current I_(s).

FIGS. 10A–10M describe an alternative embodiment for constructing an MRelement which has a dual stripe MR sensor which can be substituted forthe single stripe MR sensor. In this embodiment the formation of thehorizontal component 64, shown in FIG. 7F, will be postponed. The firststep in the construction of the dual stripe MR sensor embodiment is toplace photoresist 200 for appropriately locating the MR sensor and thenforming a layer of spacer material 202. Top portions of the spacermaterial 202 are then removed by milling and the photoresist 200 isremoved leaving a fence of spacer 204 as shown in FIG. 10B. MR material206 is then deposited on the top and the sides of the spacer 204 afterwhich the top MR material is removed by milling, as shown in FIG. 10D,leaving MR stripes 208 and 210. It should be noted that by this singledeposition the MR stripes 208 and 210 will be nearly identical so thatthey can implement near absolute common mode rejection.

Active regions of the MR stripes 208 and 210 are then protected byphotoresist layers 212 and 213, as shown in FIGS. 10E and 10F. Hard biasand lead material 214 is then formed after which the photoresist layers212 and 213 are removed. Photo-resist layers 215 and 216 are thenplaced, as shown in FIGS. 10G and 10H, for protecting the hard bias andlead material to be retained and all other hard bias and lead materialis milled away leaving hard bias and leads 217, 218, 219 and 220 asshown in FIG. 10G. Second gap material 221 is then deposited over theentire wafer, as shown in FIG. 10I. Photoresist layers 222 and 223 arethen placed, as shown in FIG. 10J, for protecting second gap material tobe retained and all other gap material is milled away, as shown in FIG.10J, leaving gap layers 224 and 225. Shield material 226 is thendeposited, as shown in FIG. 10K. Photoresist layers 228 and 230 are thenformed, as shown in FIG. 10L, to protect shield material to be retainedand all other shield material is removed by milling, as shown in FIG.10L. The photoresist layers 228 and 230 are then removed leaving thefinal MR head structure with a dual stripe and first and second shields232 and 234, as shown in FIG. 10M. The shield 234 can be a common layerwith the horizontal component 64 of the first pole piece as shown inFIG. 5. The structure encompassed by the numeral 80 would be substitutedfor the single stripe MR sensor 80, shown in FIG. 5, to provide thesecond embodiment of the invention employing the dual stripe MR sensor.

Conductors for the dual stripe MR sensor are shown in FIG. 11.Conductors 236 and 238 may be connected to opposite ends of one or moreof the lead layers 52 with the conductor 236 connected to ground and theconductor 238 receiving current I. Conductors 240 and 242 may beconnected at first ends to respective ends of the MR stripes 208 and 210and conductors 244 and 246 may be connected at first ends to oppositeends of the MR stripes 208 and 210. Second ends of the conductors 240and 242 may be connected to ground. A second end of the conductor 244may receive a first sense current I_(s1) and a second end of theconductor 246 may receive an identical sense current I_(s2). Thecurrents may be conducted through the MR sensors 208 and 210 withopposite polarity or they may be conducted therethrough with the samepolarity and then processed by a differential amplifier to implementcommon mode rejection of noise. The second embodiment of the presentinvention has the advantages of both aspects of the invention, namelylocation of the MR sensor at the ABS of a horizontal head and employingnear identical MR stripes of a dual MR sensor for near absolute commonmode rejection of noise.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

1. A method of making a horizontal magnetic head having a planar headsurface, comprising the steps of: forming at least one coil layer and aninsulation stack with the coil layer being embedded in the insulationstack; forming first and second pole pieces with the insulation stacksandwiched between the first and second pole pieces; forming the firstpole piece with a first horizontal component which is partially boundedby first and second major planar thin film surfaces joined by a firstedge with the first major planar thin film surface of the firsthorizontal component forming a portion of the planar head surface;forming the first pole piece with a first recessed horizontal componentwhich is recessed from and extends parallel to the planar head surface;forming the first pole piece with a slanted component which extends atan angle to an ABS and joins the first recessed horizontal component andthe first horizontal component; forming the second pole piece with asecond horizontal component which is partially bounded by first andsecond major planar thin film surfaces joined by a second edge with thefirst major planar thin film surface of the second horizontal componentforming a portion of the planar head surface; forming a write gap layerbetween said first and second edges; forming a first shield layer havingfirst and second major planar thin film surfaces joined by a third edgewith the first major planar thin film surface of the first shield layerforming a portion of the planar head surface; forming a magnetoresistive(MR) sensor and first and second gap layers with the MR sensorsandwiched between the first and second gap layers and the first andsecond gap layers located between the third edge and the firsthorizontal component and with the MR sensor and the first and second gaplayers forming portions of the planar head surface; and forming aninsulation layer between the MR sensor, the first and second gap layer,the first shield layer, the first horizontal component and the firstrecessed horizontal component so as to separate the MR sensor, the firstand second gap layers, the first shield layer and the first horizontalcomponent from the first recessed horizontal component.
 2. A methodaccording to claim 1, comprising: forming the MR sensor with an activeregion wherein the active region has a width which defines a read trackwidth; forming each of the first and second horizontal components with awidth at said write gap layer which defines a write track width; andaligning the widths of the active region and the first and secondhorizontal components.
 3. A method according to claim 2, comprising:said forming of the first horizontal component forming the firsthorizontal component with a fourth edge which interfaces the second gaplayer so that the first horizontal component serves as a second shieldlayer for the MR sensor; forming the second pole piece with a secondrecessed horizontal component which is recessed from and extendsparallel to the ABS; and joining the second horizontal component to thesecond recessed horizontal component with the second major planar thinfilm surface of the second horizontal component overlapping andinterfacing the first major planar thin film surface of the secondrecessed horizontal component.